1. Field of the Invention
The present invention relates to a liquid biocidal composition containing (a) formaldehyde adduct compounds and (b) an isothiazolone, which is intended to provide synergistic biocidal. activity against bacteria and fungi. More particularly, the present invention relates to the use of a biocide composition which includes formaldehyde adduct compounds and 1,2- benzisothiazolin-3-one.
2. Description of the Prior Art
Synergistic biological activity exists when the combination of lesser quantities of two biocidal agents results in an equal or greater inhibitory effect than is achieved by the use of either agent acting alone. The synergistic interaction of two or more antimicrobial agents produces an effect that is more than additive in its resultant biological activity.
Formaldehyde adduct compounds are known biocides; their proposed biological target is the cell wall of susceptible microorganisms (S. P. Denyer, 1990. Mechanisms of action of biocides. International Biodeterioration, 26:89). Examples of such adduct compounds includeN-methyl-2-hydroxymethyleneoxypropyl-2xe2x80x2-hydroxypropylamineanditsformaldehyde oligomers (manufactured by Creanova Inc., Somerset, N. J. under the trademark NUOSEPT(copyright) 145, hereinafter xe2x80x9cNMPFAxe2x80x9d); oxazolidines such as (4,4-dimethyloxazolidine, manufactured by Creanova Inc. under the trademark NUOSEPT(copyright) 101, hereinafter xe2x80x9cDMOxe2x80x9d), mixtures of bicyclic oxazolidines (such as (5-hydroxymethoxymethyl-1-aza-3,7-dioxabicyclo(3.3.0) octane,5-hydroxymethyl-1-aza-3,7-dioxabicyclo(3.3.0)octane,5-hydroxypoly[methyleneoxy-methyl-1-aza-3,7-dioxabicyclo (3.3.0) octane; manufactured by Creanova Inc. under the trademark NUOSEPT(copyright) 95, hereinafter xe2x80x9cMBOxe2x80x9d; and 2-[(hydroxymethyl) amino]ethanol, (manufactured by Creanova Inc. under the trade mark NUOSEPT(copyright) 91, hereinafter xe2x80x9cHMAExe2x80x9d).
The compound 1,2-benzisothiazolin-3-one (hereinafter xe2x80x9cBITxe2x80x9d), an isothiazolone, is an antimicrobial agent. Isothiazolones are disclosed in U.S. Pat. Nos. 3,761,488; 4,105,431; 4,252,694; 4,265,899; 4,279,762; 4,871,754, and 5,620,997. Studies on the microbiological target of BIT suggest that the compound acts on the cytoplasmic membrane thiol-enzymes. (See, e.g., Fuller, S. J., Denyer, S. P., Hugo, W. B., Pemberton, D., Woodcock, P. M. and Buckley, A. J., (1985). The mode of action of 1,2-benzisothiazolin-3-one on Staphylococcus aureus, Letters in Applied Microbiology, 1, 13-15.)
Biocidal combinations with synergistic activities for various microorganisms are known. Different formaldehyde donor compounds have been combined with 3-iodo-2-propynyl butyl carbamate (IPBC), a well known fungicide, to broaden the antimicrobial spectrum of activity. (U.S. Pat. No. 5,428,050; U.S. Pat. No. 4,844,891; D. Pendelton et al. (1987), Modern Paint and Coatings August p:30; September, p:148.) Also, biocidal combinations containing an isothiazolone and other compounds have been disclosed. Some synergistic combinations include isothiazolones and metal complex with functional ligands (U.S. Pat. No. 4,608,183); isothiazolones and hydroxymethylamino acetic acids (U.S. Pat. No. 4,980,176); isothiazolones and substituted anilides (U.S. Pat. No. 5,212,193); and, isothiazolones and triazines (U.S. Pat. No. 5,294,614).
It is an object of the present invention to provide a synergistic biocidal combination, which is more efficacious than known microbicidal compositions.
Another object of the present invention is the provision of a synergistic combination of biocides which is water-soluble and can be uniformly distributed.
Still another object of this invention is the provision of a water-soluble preservative mixture for use in architectural coating applications (i.e. paints, stains) and other coating related materials (adhesives, sealants, joint compounds, latex emulsions, etc), which is effective against a wide range of fungi and bacteria.
It has been found that the composition of the present invention comprising a mixture of a formaldehyde adduct compound and an isothiazolone exhibits synergistic antimicrobial activity against a wide range of microorganisms; the biological activity of the two compounds acting together being greater than the sum of both compounds acting separately. Synergistic antimicrobial activity may be the result of each biocide having a different mechanism of action on the target microorganisms. The advantages of using a synergistic combination include:
a.) a broadened antimicrobial spectrum of activity;
b.) an increase in effectiveness;
c.) a reduction of the use levels; and
d.) a decrease in the toxicity of a given agent to the host and the environment.
The present invention, which combines formaldehyde adduct compounds and 1,2-benziosthiazolin-3-one (BIT), provides a composition having synergistic activity against a wide range of bacteria and fungi.
The present invention is directed to a mixture of two biocides designed to control unwanted bacterial and fungal growth in water-based applications, including but not limited to, paints, e.g., acrylics, polyvinyl acetates, styrene-butadienes, etc., coatings, adhesives, sealants, latex emulsions and joint compounds. The liquid biocidal composition of the present invention comprise a mixture of formaldehyde adducts, including NMPFA, DMO, MBO or HMAE, and BIT. The weight ratio of the formaldehyde adduct compound to BIT in the composition of the present invention ranges from about 100:1 to 1:100, more preferably from about 30:1 to 1:30, and most preferably from about 6:1 to 1:6. The BIT can be in the form of an acid or base.
The synergistic antimicrobial activity of the present invention is demonstrated by testing over a range of concentrations and ratios of NMPFA and BIT. The synergistic antimicrobial activity of the present invention is also demonstrated by testing the formaldehyde adduct compounds DMO, MBO or HMAE, and BIT. The examples presented below serve to illustrate the invention and to demonstrate the synergistic results obtained when the two compounds are used in combination, as compared with their effectiveness when used individually.